Patent GB-507366-A (GB)
Title: Process for synthesising hydrocarbons from carbon monoxide and hydrogen
IPC: C07C1/04
Filed: 1938-04-25
Abstract: 507,366. Hydrocarbon synthesis. METALLGES. AKT.-GES., and HERBERT, W. April 25, 1938, No. 12397. [Class 2 (iii)] In a process for the synthesis of hydrocarbons, mainly paraffinic and olefinic, from carbon monoxide and hydrogen with catalysts known for the synthesis of benzine, oil, and solid paraffin and at temperatures below those yielding only methane, the gas throughput is kept greater than I litre (measured at N.T.P.) preferably 2-20 litres or more per hour per gram of hydrogenating metal in the contact mass, and the reaction chamber or the pressure or both is made so large that the time of contact of the gas with the contact mass is greater than 45 secs., for example 1-10 mins., while the temperature is so regulated that the heat generated, calculated as heat load per square metre of cooling surface of the cooling members embedded in the contact mass, at the gas pressure of p atmospheres, does not exceed 500 3#p kilogram calories per hour. The throughput and time of stay are first adjusted and the temperature gradually increased, e.g. from 150‹ C., but always keeping it below that value at which the heat of reaction exceeds the specified limit, to give an optimum yield of liquid hydrocarbons. The ratio between time of stay in mins. and gas throughput in N.T.P. litres per gr. of hydrogenating metal per hr. is generally kept greater than 1:1, e.g. from 3 to 10 : 1. When working at atmospheric pressure, the gas throughput may be doubled, for example, while using the same amount of contact material, by at least doubling the volume of the contact chamber and the area of the cooling surfaces, the contact mass being increased in volume by insertion of wire spirals or Raschig rings or addition of large amounts of carrier materials, e.g. kieselguhr, active carbon or pumice. Such increase in volume can only be employed up to a quintuple enlargement of the initial poured volume of the catalyst. The usual contact material containing 33 per cent of cobalt may be diluted with kieselguhr to less than 25 per cent cobalt so that 1 litre of poured volume contains preferably 10 to 40 g. hydrogenating metal. Material, containing only 2 per cent of cobalt is particularly suitable for the synthesis of lower hydrocarbons from benzine down to gasol. Elevated pressures, e.g. 3-20 atmos. may be used. Higher pressure up to 100 atmos. or more can be employed, but if catalysts containing cobalt, nickel or copper which catalyse the reaction CO + 2H2=CH2 + H2O are used, working is effected in a plurality of stages or with recycling of the gas, conditions being regulated so that the dew point of water vapour is not reached. Recycling of gases, if desired after removal of reaction products, increases the catalyst life and reduces the formation of solid puraffin. The quantity recycled and the temperature are suitably chosen so that the hydrogen partial pressure of the gas, at pressure p, is less than 0À3 Î p<0.9> atmos. Gases containing an excess of carbon monoxide can then be utilized. In examples : (1) a cobalt-thoriumkieselguhr catalyst, prepared by precipitating a mixture of the metal nitrate solutions and kieselguhr with potassium carbonate, granulating and reducing, and containing 33.per cent cobalt, 6 per cent thoria, and 61 per cent kieselguhr is used. The contact chamber is divided into two stages, part of the reaction products being withdrawn intermediately. Gases containing 2 vols. of H2 to 1 of CO are reacted at 180‹C. and normal pressure, the throughput being 11. per hr. per gram of cobalt, the time of stay 36 secs., and the heat load per sq. m., 240 kg. cals. per hr. The yield is 100 g. per cm. of gas. By using a chamber of twice the capacity and the same amount of catalyst diluted to twice the volume, the throughput is increased to 1À4 1., and the time of stay to 51À5 secs., the heat load is 168 kg. cals., and the . yield is the same. The temperature is preferably a little higher, e.g. 185‹ C.; (2) the catalyst is made as in (1) but using twice the volume of kieselguhr, and is placed in the chamber used in the second part of that example. With the same throughput and time of stay the yield is 110 g. having a higher benzine content ; (3) the amount of kieselguhr in the catalyst and the chamber capacity. are further doubled. With the same throughput, and time of stay 103 secs., the yield becomes 115 g. ; (4) the catalyst of (2) is used in a contact chamber at 195‹ C. and 12 atmos. The throughput is 2 1., the time of stay 7À2 mins. and the yield 130 g.; (5) end gases from the process of (4) are recycled in amount equal to twice that of the fresh gas. At 200‹ C. the same yield is obtained but of higher benzine content ; (6) synthesis gas with five times its volume of recycle gas is treated at 220‹ C. and 100 atmos. using a catalyst containing 5 per cent of cobalt. The throughput is 101., the time of stay 50 mins., the heat load 588 kg. cals., and the yield 145 g.; (7) the throughput of (6) is trebled and the recycled volume quintupled. At 240‹ C. the yield is 140 g. and the heat load is now 1750 kg. cals. ; (8) the throughput is further doubled and the temperature raised to 255‹ C. to give the same relative conversion. The yield is only 70 g. apart from methane and CO2. The heat load is 3600 kg. cals., which exceeds the limit of 500<3>#p.